BQ500412RGZT

bq500412 www.ti.com SLUSBO2A – NOVEMBER 2013 – REVISED DECEMBER 2013 Low System Cost, Wireless Power Controller for WPC TX A6 Check for Samples: bq500412 FEATURES DESCRIPTION • The bq500412 is a Qi-certified value solution that integrates all functions required to control wireless power delivery to a single WPC1.1 compliant receiver. It is WPC1.1 compliant and designed for 12V systems, or 5-V systems with an optional boost converter, as a wireless power consortium type A6 free positioning transmitter. The bq500412 pings the surrounding environment for WPC compliant devices to be powered, safely engages the device, receives packet communication from the powered device and manages the power transfer according to WPC1.1 specification. To maximize flexibility in wireless power control applications, Dynamic Power Limiting™ (DPL) is featured on the bq500412 when used with an optional boost converter from a 5-V input. Dynamic Power Limiting™ enhances user experience by seamlessly optimizing the usage of power available from limited input supplies. The bq500412 supports both Foreign Object Detection (FOD) and enhanced Parasitic Metal Object Detection (PMOD) for legacy product by continuously monitoring the efficiency of the established power transfer, protecting from power lost due to metal objects misplaced in the wireless power transfer field. Should an abnormal operating condition develop during power transfer, the bq500412 handles it and provides indicator outputs. Comprehensive status and fault monitoring features enable a low cost yet robust, Qi-certified wireless power system design. 1 2 • • • • • • Proven, Qi-Certified WPC1.1 Solution for Transmit-Side Application (suitable for 1, 2 or 3 coil configurations) Lowest Device Count for Full WPC1.1 12-V A6 Solution (single driver stage for all coils) New Standby Scheme Reduces Standby and Sleep Power Without Need for Extra Supervisor Circuit Improved FOD Calibration Scheme Simplifies Certification and Increases Accuracy at Higher Power (customer configurable) Dynamic Power Limiting™ for USB and Limited Power Source Operation When Used With 5-V Input Digital Demodulation Removes Need for External Filter Circuitry 10 Configurable LED modes Indicate Charging State and Fault Status APPLICATIONS • • Wireless Power Consortium (WPC1.1) Compliant Wireless Chargers For: – Qi-Certified Smart Phones and Other Handhelds – Car and Other Vehicle Accessories See www.ti.com/wirelesspower for More Information on TI's Wireless Charging Solutions The bq500412 is available in a 48-pin, 7-mm x 7-mm QFN package. System Diagram and Efficiency Versus System Output Power 12 V Input 70 Current Sense WPC A 6 Coil Assembly BQ500412 HalfBridge Stage 60 Efficiency (%) 3.3 VDC Regulator 80 50 40 30 20 COMM Signal 10 Coil Select 0 0 0.5 1 1.5 2 2.5 3 3.5 4 Power (W) 4.5 5 C001 1 2 Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. Dynamic Power Limiting is a trademark of Texas Instruments. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright © 2013, Texas Instruments Incorporated bq500412 SLUSBO2A – NOVEMBER 2013 – REVISED DECEMBER 2013 www.ti.com These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. ORDERING INFORMATION (1) OPERATING TEMPERATURE RANGE, TA ORDERABLE PART NUMBER PIN COUNT SUPPLY PACKAGE TOP SIDE MARKING BQ500412RGZR 48 pin Reel of 2500 QFN BQ500412 BQ500412RGZT 48 pin Reel of 250 QFN BQ500412 -40°C to 110°C (1) For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TI web site at www.ti.com. ABSOLUTE MAXIMUM RATINGS (1) over operating free-air temperature range (unless otherwise noted) VALUE MIN MAX Voltage applied at V33D to GND –0.3 3.6 Voltage applied at V33A to GND –0.3 3.6 –0.3 3.6 –40 150 Voltage applied to any pin (2) Storage temperature,TSTG (1) (2) 2 UNIT V °C Stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. These are stress ratings only and functional operation of the device at these or any other conditions beyond those indicated under recommended operating conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. All voltages referenced to GND. Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: bq500412 bq500412 www.ti.com SLUSBO2A – NOVEMBER 2013 – REVISED DECEMBER 2013 RECOMMENDED OPERATING CONDITIONS over operating free-air temperature range (unless otherwise noted) MIN V Supply voltage during operation, V33D, V33A 3.0 TA Operating free-air temperature range –40 TJ Junction temperature TYP MAX 3.3 UNIT 3.6 110 110 V °C THERMAL INFORMATION bq500412 THERMAL METRIC (1) RGZ UNITS 48 PINS θJA Junction-to-ambient thermal resistance (2) 28.4 θJCtop Junction-to-case (top) thermal resistance (3) 14.2 (4) θJB Junction-to-board thermal resistance ψJT Junction-to-top characterization parameter (5) 0.2 ψJB Junction-to-board characterization parameter (6) 5.3 θJCbot Junction-to-case (bottom) thermal resistance (7) 1.4 (1) (2) (3) (4) (5) (6) (7) 5.4 °C/W For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953. The junction-to-ambient thermal resistance under natural convection is obtained in a simulation on a JEDEC-standard, high-K board, as specified in JESD51-7, in an environment described in JESD51-2a. The junction-to-case (top) thermal resistance is obtained by simulating a cold plate test on the package top. No specific JEDECstandard test exists, but a close description can be found in the ANSI SEMI standard G30-88. The junction-to-board thermal resistance is obtained by simulating in an environment with a ring cold plate fixture to control the PCB temperature, as described in JESD51-8. The junction-to-top characterization parameter, ψJT, estimates the junction temperature of a device in a real system and is extracted from the simulation data for obtaining θJA, using a procedure described in JESD51-2a (sections 6 and 7). The junction-to-board characterization parameter, ψJB, estimates the junction temperature of a device in a real system and is extracted from the simulation data for obtaining θJA , using a procedure described in JESD51-2a (sections 6 and 7). The junction-to-case (bottom) thermal resistance is obtained by simulating a cold plate test on the exposed (power) pad. No specific JEDEC standard test exists, but a close description can be found in the ANSI SEMI standard G30-88. Spacer Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: bq500412 3 bq500412 SLUSBO2A – NOVEMBER 2013 – REVISED DECEMBER 2013 www.ti.com ELECTRICAL CHARACTERISTICS over operating free-air temperature range (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX V33A = 3.3 V 8 15 V33D = 3.3 V 44 55 V33D = V33A = 3.3 V 52 60 3.3 3.6 4 4.6 UNIT SUPPLY CURRENT IV33A IV33D Supply current ITOTAL mA INTERNAL REGULATOR CONTROLLER INPUTS/OUTPUTS V33 3.3-V linear regulator V33FB 3.3-V linear regulator feedback IV33FB Series pass base drive Beta Series NPN pass device Emitter of NPN transistor 3.25 VIN = 12 V; current into V33FB pin 10 V mA 40 EXTERNALLY SUPPLIED 3.3 V POWER V33D Digital 3.3-V power TA = 25°C 3 3.6 V33A Analog 3.3-V power TA = 25°C 3 3.6 V33Slew V33 slew rate V33 slew rate between 2.3 V and 2.9 V, V33A = V33D 0.25 V V/ms DIGITAL DEMODULATION INPUTS COMM_A+, COMM_A-, COMM_B+, COMM_BVbias COMM+ Bias Voltage COMM+, COMM- 1.0 Modulation voltage digital resolution REA Input impedance Ground reference 0.5 IOFFSET Input offset current 1-kΩ source impedance –5 V 1 1.5 mV 3 MΩ 5 µA 0.36 V ANALOG INPUTS V_SENSE, I_SENSE, T_SENSE, LED_MODE, LOSS_THR, SNOOZE_CAP, PWR_UP VADDR_OPEN Voltage indicating open pin LED_MODE open VADDR_SHORT Voltage indicating pin shorted to GND LED_MODE shorted to ground VADC_RANGE Measurement range for voltage monitoring ALL ANALOG INPUTS INL ADC integral nonlinearity RIN Input impedance CIN Input capacitance Ground reference 2.37 0 2.5 -2.5 2.5 8 mV MΩ 10 pF DIGITAL INPUTS/OUTPUTS DGND1 + 0.25 VOL Low-level output voltage IOL = 6 mA , V33D = 3 V VOH High-level output voltage IOH = -6 mA , V33D = 3 V VIH High-level input voltage V33D = 3V VIL Low-level input voltage V33D = 3.5 V IOH(MAX) Output high source current 4 IOL(MAX) Output low sink current 4 V33D - 0.6V 2.1 V 3.6 1.4 mA SYSTEM PERFORMANCE VRESET Voltage where device comes out of reset V33D Pin tRESET Pulse width needed for reset RESET pin fSW Switching Frequency 4 2.4 2 112 Submit Documentation Feedback V µs 205 kHz Copyright © 2013, Texas Instruments Incorporated Product Folder Links: bq500412 bq500412 www.ti.com SLUSBO2A – NOVEMBER 2013 – REVISED DECEMBER 2013 DEVICE INFORMATION Functional Block Diagram bq500412 LED Control / Low Power Interface COMM_A+ 37 COMM_A- 38 COMM_B+ 39 6 PMOD 7 LED_A 8 LED_B 9 SLEEP 22 FOD_CAL 25 LED_C Digital Demodulation 18 SNOOZE 13 FOD COMM_B- 40 12 PWM-A Controller PWM 15 COIL_1 16 COIL_2 COIL_PEAK 1 17 COIL_3 V_SENSE 45 I_SENSE 42 T_SENSE 2 12-bit ADC 23 BUZ_AC Buzzer Control 24 BUZ_DC LOSS_THR 43 LED_MODE 44 SNOOZE_CAP POR 11 DATA I2C 3 10 CLK 5 RESET Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: bq500412 5 bq500412 SLUSBO2A – NOVEMBER 2013 – REVISED DECEMBER 2013 www.ti.com COMM_A+ COMM_B- I_SENSE V_SENSE V_SENSE 37 36 GND 48 47 46 45 44 43 42 41 40 39 38 ADCREF COMM_A- COMM_B+ RESERVED LOSS_THR LED_MODE RGZ Package (Top View) GND COIL_PEAK 1 T_SENSE 2 35 BPCAP SNOOZE_CAP 3 34 V33A PWR_UP 4 33 V33D RESET 5 32 GND PMOD 6 31 GND bq500412 LED_A 7 30 RESERVED LED_B 8 29 RESERVED SLEEP 9 28 RESERVED CLK 10 27 RESERVED DATA 11 26 RESERVED 6 Submit Documentation Feedback LED_C BUZ_DC BUZ_AC FOD_CAL SNOOZE_CHG RESERVED RESERVED SNOOZE COIL_3 COIL_2 COIL_1 RESERVED 25 12 13 14 15 16 17 18 19 20 21 22 23 24 FOD PWM_A Copyright © 2013, Texas Instruments Incorporated Product Folder Links: bq500412 bq500412 www.ti.com SLUSBO2A – NOVEMBER 2013 – REVISED DECEMBER 2013 PIN FUNCTIONS PIN NO. 1 NAME I/O DESCRIPTION COIL_PEAK I Connected to peak detect circuit. Protects from coil overvoltage event. T_SENSE I Sensor Input. Device shuts down when below 1 V for longer than 150ms. If not used, keep above 1 V by connecting to the 3.3-V supply. 3 SNOOZE_CAP I Connected to interval timing capacitor 4 PWR_UP I First power-up indicator 5 RESET I Device reset. Use a 10-kΩ to 100-kΩ pull-up resistor to the 3.3-V supply. 6 PMOD O Select for PMOD threshold 7 LED_A I Connect to an LED via 470-Ω resistor for status indication. Typically GREEN 8 LED_B I Connect to an LED via 470-Ω resistor for status indication. Typically RED 2 9 SLEEP O Force SLEEP (5 sec low power) 10 CLK I/O 10-kΩ pull-up resistor to 3.3-V supply. Please contact field for GUI application assitance. 11 DATA I/O 10-kΩ pull-up resistor to 3.3-V supply. Please contact field for GUI application assitance. PWM_A O PWM Output A, controls one half of the full bridge in a phase-shifted full bridge. Switching deadtimes must be externally generated. 13 FOD O Select for FOD threshold 14 RESERVED O Reserved. Leave open. 15 COIL_1 O Select first coil 16 COIL_2 O Select second coil 17 COIL_3 O Select third coil 18 SNOOZE O Force SNOOZE (500ms low power) 19 RESERVED O Reserved, leave this pin open. 20 RESERVED I Reserved, connect to GND. 21 SNOOZE_CHG O Charge the snooze cap 22 FOD_CAL O Select for FOD calibration resistor 23 BUZ_AC O AC Buzzer Output. Outputs a 400-ms, 4-kHz AC pulse when charging begins. BUZ_DC O DC Buzzer Output. Outputs a 400-ms DC pulse when charging begins. This could also be connected to an LED via 470-Ω resistor. 25 LED_C I/O Connect to an LED via 470-Ω resistor for status indication. Typically YELLOW 26 RESERVED I/O Reserved, connect to GND. 27 RESERVED I/O Reserved, leave this pin open. 28 RESERVED I/O Reserved, leave this pin open. 29 RESERVED I/O Reserved, leave this pin open. 30 RESERVED I/O Reserved, leave this pin open. 31 GND I/O Reserved, connect to GND. 12 24 Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: bq500412 7 bq500412 SLUSBO2A – NOVEMBER 2013 – REVISED DECEMBER 2013 www.ti.com PIN FUNCTIONS (continued) PIN NO. 32 33 34 GND V33D V33A I/O DESCRIPTION — GND. — Digital core 3.3-V supply. Be sure to decouple with bypass capacitors as close to the part as possible. — Analog 3.3-V Supply. This pin can be derived from V33D supply, decouple with 10-Ω resistor and additional bypass capacitors 35 BPCAP — Bypass capacitor for internal 1.8-V core regulator. Connect bypass capacitor to GND. 36 GND — GND. 37 COMM_A+ I Digital demodulation non-inverting input A, connect parallel to input B+. 38 COMM_A- I Digital demodulation inverting input A, connect parallel to input B-. 39 COMM_B+ I Digital demodulation non-inverting input B, connect parallel to input A+. 40 COMM_B- I Digital demodulation inverting input B, connect parallel to input A-. 41 RESERVED O Reserved, leave this pin open. I Transmitter input current, used for efficiency calculations. Use 20-mΩ sense resistor and A=50 gain current sense amplifier. 42 I_SENSE 43 LOSS_THR I Input to program FOD/PMOD thresholds and FOD_CAL correction. 44 LED_MODE I Input to select from four LED modes. I Transmitter input voltage, used for efficiency calculations. Use 76.8-kΩ to 10-kΩ divider to minimize quiescent current. I System input voltage, used for DPL. Use 76.8-kΩ to 10-kΩ divider to minimize quiescent current. 45 46 8 NAME V_SENSE V_IN 47 GND 48 ADCREF 49 EPAD — I — GND. External Reference Voltage Input. Connect this input to GND. Flood with copper GND plane and stitch vias to PCB internal GND plane. Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: bq500412 bq500412 www.ti.com SLUSBO2A – NOVEMBER 2013 – REVISED DECEMBER 2013 Principles of Operation Fundamentals The principle of wireless power transfer is simply an open cored transformer consisting of primary and secondary coils and associated electronics. The primary coil and electronics are also referred to as the transmitter, and the secondary side the receiver. The transmitter coil and electronics are typically built into a charger pad. The receiver coil and electronics are typically built into a portable device, such as a cell-phone. When the receiver coil is positioned on the transmitter coil, magnetic coupling occurs when the transmitter coil is driven. The flux is coupled into the secondary coil which induces a voltage, current flows, it is rectified and power can be transferred quite effectively to a load - wirelessly. Power transfer can be managed via any of various familiar closed-loop control schemes. Wireless Power Consortium (WPC) The Wireless Power Consortium (WPC) is an international group of companies from diverse industries. The WPC standard was developed to facilitate cross compatibility of compliant transmitters and receivers. The standard defines the physical parameters and the communication protocol to be used in wireless power. For more information, go to www.wirelesspowerconsortium.com. Power Transfer Power transfer depends on coil coupling. Coupling is dependent on the distance between coils, alignment, coil dimensions, coil materials, number of turns, magnetic shielding, impedance matching, frequency and duty cycle. Most importantly, the receiver and transmitter coils must be aligned for best coupling and efficient power transfer. The closer the space between the coils, the better the coupling, but the practical distance is set to be less than 5 mm (as defined within the WPC Specification) to account for housing and interface surfaces. Shielding is added as a backing to both the transmitter and receiver coils to direct the magnetic field to the coupled zone. Magnetic fields outside the coupled zone do not transfer power. Thus, shielding also serves to contain the fields to avoid coupling to other adjacent system components. Regulation can be achieved by controlling any one of the coil coupling parameters. For WPC compatibility, the transmitter coils and capacitance are specified and the resonant frequency point is fixed. Power transfer is regulated by changing the operating frequency between 120 kHz to 205 kHz. The higher the frequency, the further from resonance and the lower the power. Duty cycle remains constant at 50% throughout the power band and is reduced only once 205 kHz is reached. The WPC standard describes the dimension and materials of the coils. It also has information on tuning the coils to resonance. The value of the inductor and resonant capacitor are critical to proper operation and system efficiency. Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: bq500412 9 bq500412 SLUSBO2A – NOVEMBER 2013 – REVISED DECEMBER 2013 www.ti.com Communication Communication within the WPC is from the receiver to the transmitter, where the receiver tells the transmitter to send power and how much. In order to regulate, the receiver must communicate with the transmitter whether to increase or decrease frequency. The receiver monitors the rectifier output and using Amplitude Modulation (AM), sends packets of information to the transmitter. A packet is comprised of a preamble, a header, the actual message and a checksum, as defined by the WPC standard. The receiver sends a packet by modulating an impedance network. This AM signal reflects back as a change in the voltage amplitude on the transmitter coil. The signal is demodulated and decoded by the transmitter side electronics and the frequency of its coil drive output is adjusted to close the regulation loop. The bq500412 features internal digital demodulation circuitry. The modulated impedance network on the receiver can either be resistive or capacitive. Figure 1 shows the resistive modulation approach, where a resistor is periodically added to the load and also shows the resulting change in resonant curve which causes the amplitude change in the transmitter voltage indicated by the two operating points at the same frequency. Figure 2 shows the capacitive modulation approach, where a capacitor is periodically added to the load and also shows the resulting amplitude change in the transmitter voltage. Rectifier Receiver Coil Receiver Capacitor Amax Modulation Resitor Operating state at logic “0” A(0) Operating state at logic “1” A(1) Comm Fsw a) F, kHz b) Figure 1. Receiver Resistive Modulation Circuit Rectifier Receiver Coil Receiver Capacitor Modulation Capacitors Amax Comm A(0) Operating state at logic “ 0” A(1) Operating state at logic “ 1” Fsw F, kHz Fo(1) < Fo(0) a) b) Figure 2. Receiver Capacitive Modulation Circuit 10 Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: bq500412 bq500412 www.ti.com SLUSBO2A – NOVEMBER 2013 – REVISED DECEMBER 2013 Application Information Coils and Matching Capacitors The coil and matching capacitor selection for the transmitter has been established by WPC standard. These values are fixed and cannot be changed on the transmitter side. An up to date list of available and compatible A6 transmitter coils can be found here (Texas Instruments Literature Number SLUA649): Capacitor selection is critical to proper system operation. The total capacitance value of 147nF is required in the center coil of the resonant tank. This capacitance is not a standard value and therefore several must be combined in parallel. It is recommended to use 100nF + 47nF, as these are very commonly available. NOTE A total capacitance value of 147nF/100 V/C0G is required in the center coil and 133nF/100V/C0G in the side coils of the resonant tank to achieve the desired resonance frequency. The capacitors chosen must be rated for 100 V operation. Use quality C0G type dielectric capacitors from reputable vendors such as KEMET, MURATA or TDK. Dynamic Power Limiting™ With an optional 5-V to 12-V boost converter, a 5-V input can enable a 12-V WPC A6 transmitter. The Dynamic Power Limiting™ (DPL) feature allows operation from a 5-V supply with limited current capability (such as a USB port). When the 5-V input voltage is observed drooping, the output power is dynamically limited to reduce the load and provides margin relative to the supply’s capability. Anytime the DPL control loop is regulating the operating point of the transmitter, the LED will indicate that DPL is active. The LED color and flashing pattern are determined by the LED Table. If the receiver sends a Control Error Packet (CEP) with a negative value, (for example, to reduce power to the load), the transmitter in DPL mode will respond to this CEP via the normal WPC control loop. NOTE The power limit indication depends on the LED_MODE selected. Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: bq500412 11 bq500412 SLUSBO2A – NOVEMBER 2013 – REVISED DECEMBER 2013 www.ti.com Option Select Pins Several pins on the bq500412 are allocated to programming the FOD and PMOD Loss Threshold and the LED mode of the device. At power up, a bias current is applied to pins LED_MODE and LOSS_THR and the resulting voltage measured in order to identify the value of the attached programming resistor. FOD, PMOD and FOD_CAL pin values are enabled and read sequentially from the same LOSS_THR bias current. The values of the operating parameters set by these pins are determined using Table 2. For LED_MODE, the selected bin determines the LED behavior based on Table 1; for the LOSS_THR, the selected bin sets a threshold used for parasitic metal object detection (see Parasitic Metal Detection (PMOD) and Foreign Object Detection (FOD) section). Table 1. bq500412 LED_MODE 44 Resistors to set options LOSS_THR To 12-bit ADC 43 FOD PMOD FOD_CAL 13 6 22 Figure 3. Option Select Pin Programming LED Indication Modes The bq500412 can directly drive up to three (3) LED outputs (pin 7, pin 8 and pin 25) through a simple current limit resistor (typically 470 Ω), based on the mode selected. The current limit resistors can be individually adjusted to tune or match the brightness of the LEDs. Do not exceed the maximum output current rating of the device. The resistor in Figure 3 connected to pin 44 and GND selects the desired LED indication scheme in Table 1. • LED modes permit the use of one to three indicator LED's. Amber in the 2-LED mode is obtained by turning on both the green and red. • LEDs can be turned on solid or configured to blink either slow (approx. 1.6s period) or fast (approx. 400ms period). • Except in modes 2 and 9, the charge complete state is only maintained for 5 seconds after which it reverts to idle. This permits the processor to sleep in order to reduce standby power consumption. In other modes, external logic, such as a flip-flop, may be implemented to maintain the charge complete indication if desired. • LED modes 5 and 8 will display a sequence of red-amber-green, for 0.5 seconds when the device is first powered up. 12 Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: bq500412 bq500412 www.ti.com SLUSBO2A – NOVEMBER 2013 – REVISED DECEMBER 2013 Table 1. LED Modes OPERATIONAL STATES LED CONTROL OPTION LED SELECTION RESISTOR X < 36.5 kΩ DESCRIPTION STANDBY POWER TRANSFER CHARGE COMPLETE FAULT DYNAMIC POWER LIMITING™ FOD Warning - - - - - - LED1, green Off Blink slow On Off Blink slow Off LED2, red Off Off Off On Blink slow Blink fast LED LED1, green Reserved, do not use LED2, red LED3, amber 1 2 3 4 5 6 7 8 9 10 42.2 kΩ 48.7 kΩ 56.2 kΩ 64.9 kΩ 75 kΩ 86.6 kΩ 100 kΩ 115 kΩ 133 kΩ 154 kΩ Choice number 1 Choice number 2 Choice number 3 Choice number 4 Choice number 5 Choice number 6 Choice number 7 Choice number 8 Choice number 9 Choice number 10 LED3, amber - - - - - - LED1, green On Blink slow On Off Blink slow Off Blink fast LED2, red On Off Off On Blink slow LED3, amber - - - - - - LED1, green Off On Off Blink fast On On - LED2, red - - - - - LED3, amber - - - - - - LED1, green Off On Off Off Off Off Blink fast LED2, red Off Off Off On Blink slow LED3, amber - - - - - - LED1, green Off Off On Off Off Off LED2, red Off On Off Off On On LED3, amber Off Off Off Blink slow Off Off LED1, green Off Blink slow On Off Off Off LED2, red Off Off Off On Off Blink fast LED3, amber Off Off Off Off Blink Slow Off LED1, green Off Blink slow Off Off Off Off LED2, red Off Off On Off Off Off LED3, amber Off Off Off On Blink slow Blink fast LED1, green Off Off On Blink slow Off Off LED2, red Off On Off Blink slow On On LED3, amber - - - - - - LED1, green Off Blink slow On Off Blink slow Off Blink fast LED2, red Off Off Off On Blink slow LED3, amber - - - - - - LED1, green Off On Off Blink fast Blink slow On LED2, red Off Off On Off Off Off LED3, amber - - - - - - Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: bq500412 13 bq500412 SLUSBO2A – NOVEMBER 2013 – REVISED DECEMBER 2013 www.ti.com Parasitic Metal Object Detect (PMOD), Foreign Object Detection (FOD) and FOD Calibration The bq500412 supports improved FOD (WPC1.1) and enhanced PMOD (WPC 1.0) features. Continuously monitoring input power, known losses, and the value of power reported by the RX device being charged, the bq500412 can estimate how much power is unaccounted for and presumed lost due to metal objects placed in the wireless power transfer path. If this unexpected loss exceeds the threshold set by the FOD or PMOD resistors, a fault is indicated and power transfer is halted. Whether the FOD or the PMOD algorithm is used is determined by the ID packet of the receiver being charged. As the default, both PMOD and FOD resistors should set a threshold of 400 mW (selected by 56.2-kΩ resistors from FOD (pin 13) and PMOD(pin 6) to LOSS_THR (pin43)). 400 mW has been empirically determined using standard WPC FOD test objects (disc, ring and foil). Some tuning might be required as every system will be slightly different. The ultimate goal of the FOD feature is safety; to protect misplaced metal objects from becoming hot. Reducing the loss threshold and making the system too sensitive will lead to false trips and a bad user experience. Find the balance which best suits the application. If the application requires disabling one function or the other (or both), it is possible by leaving the respective FOD/PMOD pin open. For example, to selectively disable the PMOD function, PMOD (pin16) should be left open. NOTE Disabling FOD results in a TX solution that is not WPC compliant. Resistors of 1% tolerance should be used for a reliable selection of the desired threshold. The FOD and PMOD resistors (pin 13 and pin 6) program the permitted power loss for the FOD and PMOD algorithms respectively. The FOD_CAL resistor (pin 22), can be used to compensate for any load dependent effect on the power loss. Using a calibrated test receiver with no foreign objects present, the FOD_CAL resistor should be selected such that the calculated loss across the load range is substantially constant (within ~100 mW). After correcting for the load dependence, the FOD and PMOD thresholds should be re-set above the resulting average by approximately 400 mW in order for the transmitter to satisfy the WPC requirements on tolerated heating. Please contact TI for more information about setting appropriate FOD, PMOD, and FOD_CAL resistor values for your design. Table 2. Option Select Bins 14 BIN NUMBER RESISTANCE (kΩ) LOSS THRESHOLD (mW) 0 237 Feature Disabled Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: bq500412 bq500412 www.ti.com SLUSBO2A – NOVEMBER 2013 – REVISED DECEMBER 2013 Shut Down via External Thermal Sensor or Trigger Typical applications of the bq500412 will not require additional thermal protection. This shutdown feature is provided for enhanced applications and is not only limited to thermal shutdown. The key parameter is the 1.0 V threshold on pin 2. Voltage below 1.0 V on pin 2 for longer than 150ms causes the device to shutdown. The application of thermal monitoring via a Negative Temperature Coefficient (NTC) sensor, for example, is straightforward. The NTC forms the lower leg of a temperature dependant voltage divider. The NTC leads are connected to the bq500412 device, pin 2 and GND. The threshold on pin 2 is set to 1.0 V, below which the system shuts down and a fault is indicated (depending on LED mode chosen). To implement this feature follow these steps: 1) Consult the NTC datasheet and find the resistence vs temperature curve. 2) Determine the actual temperature where the NTC will be placed by using a thermal probe. 3) Read the NTC resistance at that temperature in the NTC datasheet, that is R_NTC. 4) Use the following formula to determine the upper leg resistor (R_Setpoint): R _ Setpoint = 2.3 ´ R _ NTC (1) The system will restore normal operation after approximately five minutes or if the receiver is removed. If the feature is not used, this pin must be pulled high. NOTE Pin 2 must always be terminated, else erratic behavior may result. 3V3_VCC Optional Temperature Sensor R_Setpoint T_SENSE NTC 2 AGND AGND Figure 4. Negative Temperature Coefficient (NTC) Application Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: bq500412 15 bq500412 SLUSBO2A – NOVEMBER 2013 – REVISED DECEMBER 2013 www.ti.com Fault Handling and Indication The following table provides approximate durations for the time before a retry is attempted for End Power Transfer (EPT) packets and fault events. Precise timing may be affected by external components, or may be shortened by receiver removal. The LED mode selected determines how the LED indicates the condition or fault. CONDITION DURATION (before retry) EPT-00 Immediate Unknown EPT-01 5 seconds Charge complete EPT-02 5 seconds Internal fault EPT-03 5 minutes temperature EPT-04 Immediate Over voltage EPT-05 Immediate Over current HANDLING EPT-06 5 seconds failure EPT-07 Not applicable Reconfiguration EPT-08 Immediate No response OC (over current) 1 minute NTC (external sensor) 5 minutes PMOD/FOD warning 12 seconds PMOD/FOD 5 minutes 10 seconds LED only, 2 seconds LED + buzzer Power Transfer Start Signal The bq500412 features two signal outputs to indicate that power transfer has begun. Pin 23 outputs a 400-ms duration, 4-kHz square wave for driving low cost AC type ceramic buzzers. Pin 24 outputs logic high, also for 400 ms, which is suitable for DC type buzzers with built-in tone generators, or as a trigger for any type of customized indication scheme. If not used, these pins can be left open. Power-On Reset The bq500412 has an integrated Power-On Reset (POR) circuit which monitors the supply voltage and handles the correct device startup sequence. Additional supply voltage supervisor or reset circuits are not needed. External Reset, RESET Pin The bq500412 can be forced into a reset state by an external circuit connected to the RESET pin. A logic low voltage on this pin holds the device in reset. For normal operation, this pin is pulled up to 3.3 VCC with a 10-kΩ pull-up resistor. Low Power Mode, SNOOZE During standby, when nothing is on the transmitter pad, the bq500412 pings the surrounding environment at fixed intervals. The ping interval can be adjusted; the component values selected for the SNOOZE circuit determine this interval between pings. Time for SNOOZE is set by an RC time constant controlling the Enable of a 3.3V LDO. The LDO will remove 3.3V from the bq500412 to reduce power. The choice of the ping interval effects two quantities: the idle efficiency of the system, and the time required to detect the presence of a receiver when it is placed on the pad. A trade off should be made which balances low power (longest ping interval) with good user experience (quick detection through short ping interval) while still meeting the WPC requirement for detection within 0.5 seconds. Typical RC time constant values for the SNOOZE circuit are 392k ohms and 4.7uF. The value can be adjusted to increase or decrease the ping interval. The system power consumption is approximately 300 mW during an active ping of all three coils, which lasts approximately 210 ms, and 40 mW for the balance of the cycle. A weighted average can thus be used to estimate the overall system’s idle consumption: If T_ping is the interval between pings in ms, P_idle in mW is approximately: (40 x (T_ping – 210) + 300 x 210)/T_ping 16 (2) Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: bq500412 bq500412 www.ti.com SLUSBO2A – NOVEMBER 2013 – REVISED DECEMBER 2013 Trickle Charge and CS100 The WPC specification provides an End-of-Power Transfer message (EPT–01) to indicate charge complete. Upon receipt of the charge complete message, the bq500412 will change the LED indication. The exact indication depends on the LED_MODE chosen. In some battery charging applications there is a benefit to continue the charging process in trickle-charge mode to top off the battery. There are several information packets in the WPC specification related to the levels of battery charge (Charge Status). The bq500412 uses these commands to enable top-off charging. The bq500412 changes the LED indication to reflect charge complete when a Charge Status message is 100% received, but unlike the response to an EPT, it will not halt power transfer while the LED is solid green. The mobile device can use a CS100 packet to enable trickle charge mode. If the reported charge status drops below 90% normal, charging indication will be resumed. Current Monitoring Requirements The bq500412 is WPC1.1 ready. In order to enable the FOD or PMOD features, current monitoring circuitry must be provided in the application design. For proper scaling of the current monitor signal, the current sense resistor should be 20 mΩ and the current shunt amplifier should have a gain of 50, such as the INA199A1. For FOD accuracy, the current sense resistor must be a quality component with 1% tolerance, at least 1/4-Watt rating, and a temperature stability of ±200 PPM. Proper current sensing techniques in the application hardware should also be observed. If WPC compliance is not required current monitoring can be omitted. Connect the I_SENSE pin (pin 42) to GND. All Unused Pins All unused pins can be left open unless otherwise indicated. Pin 4 can be tied to GND and flooded with copper to improve ground shielding. Please refer to the pin definition table for further explanations. Design Checklist for WPC1.1 Compliance with the bq500412 • • • • Coil and capacitor selection matches the A6 specification. Total 147-nF center and 133-nF side coil resonant capacitor requirement is met. Precision current sense amp used, such as the INA199A1. This is required for accurate FOD operation. Current shunt resistor 1% and